Connection shafts and drive units are common components in vehicles. The drive unit typically has an output shaft or an input shaft for receiving a joint. Typically, the drive unit is an axle, transfer case, transmission, power take-off unit or other torque device, all of which are common components in automotive vehicles. Typically, one or more joints are assembled to the shaft to form a propeller or drive shaft assembly. It is the propeller shaft assembly which is connected, for instance, at one end to the output shaft of a transmission and, at the other end, to the input shaft of a differential. The shaft is solid or tubular with ends adapted to attach the shaft to an inner race of the joint thereby allowing an outer race connection to a drive unit. The inner race of the joint is typically press-fit, splined, or pinned to the shaft making the outer race of the joint available to be bolted or press-fit to a hub connector, flange or stubshaft of the particular drive unit. At the other end of the propeller shaft, the same typical or traditional connection is made to a second drive unit when connecting the shaft between the two drive units. Optionally, the joint may be coupled to a shaft for torque transfer utilizing a direct torque flow connection.
In many off road vehicle environments considerable torque is applied through both the various shafts as well as their respective joints. All Terrain Vehicles and Utility Vehicles often have drivelines that are subject to unusually high torque values during unusual or extreme events. These events often arise when the vehicle lands after jumping off irregular terrain. The impact upon landing generates considerable torque in the drivelines. This torque is typically subsequently imparted into the individual components of the constant velocity joint. When the torque imparted into the CV joint components exceeds design considerations, the components can experience failure. A common design response to these extreme conditions has been to increase the size of the CV joint components in order to increase their maximum torque weathering capacity.
In addition to the extreme conditions, designers are utilizing higher capacity engines in vehicle designs. These higher capacity engines increase the power passed through the drivelines and therefore increase the overload torques experienced during extreme conditions. Existing methods of compensation require continued upsizing of the drivelines in order to accommodate the increased power and resulting increased overload torques. Continued upsizing, however, results in increases in mass of the driveline components with subsequent mass increases to the vehicle itself. Upsizing, therefore, poses undesirable restrictions on vehicle designers.
It would be advantageous to have a torque overload protection feature incorporated into the driveline such that component upsizing, and its negative consequences, could be avoided or minimized.